Cooling down the bath salts: Carvedilol attenuation of methylone and mephedrone mediated hyperthermia

The pharmacology and neurotoxicology of synthetic cathinones

The synthetic cathinones are man-made compounds derived from the naturally occurring drug cathinone, which is found in the khat plant. The drugs in this pharmacological class that will be the focus of this chapter include mephedrone, MDPV, methcathinone and methylone. These drugs are colloquially known as "bath salts". This misnomer suggests that these drugs are used for health improvement or that they have legitimate medical uses. The synthetic cathinones are dangerous drugs with powerful pharmacological effects that include high abuse potential, hyperthermia and hyperlocomotion. These drugs also share many of the pharmacological effects of the amphetamine class of drugs including methamphetamine, amphetamine and MDMA and therefore have high potential to cause damage to the central nervous system. The synthetic cathinones are frequently taken in combination with other psychoactive drugs such as alcohol, marijuana and the amphetamine-like stimulants, creating a situation where heightened pharmacological and neurotoxicological effects are likely to occur. Despite the structural features shared by the synthetic cathinones and amphetamine-like stimulants, including their actions at monoamine transporters and receptors, the effects of the synthetic cathinones do not always match those of the amphetamines. In particular, the synthetic cathinones are far less neurotoxic than their amphetamine counterparts, they produce a weaker hyperthermia, and they cause less glial activation. This chapter will briefly review the pharmacology and neurotoxicology of selected synthetic cathinones with the aim of delineating key areas of agreement and disagreement in the literature particularly as it relates to neurotoxicological outcomes.

Lowering of brain endothelial cell barrier function by exposure to 4'-iodo-α-pyrrolidinononanophenone

Overuse of pyrrolidinophenones (PPs) is known to cause damage to vascular and central nervous systems, but little is known about its effect on brain endothelial barrier function. In this study, we found that exposure to 4'-iodo-α-pyrrolidinononanophenone (I-α-PNP), one of the most potently cytotoxic PPs, at sublethal concentrations decreases trans-endothelial electrical resistance and increases paracellular permeability across a monolayer of human brain microvascular endothelial cells. Treatment with I-α-PNP also elevated the production of superoxide anion. Furthermore, the treatment reduced the expression and plasma membrane localization of a tight junction protein claudin-5 (CLDN5), which was almost restored by pretreatment with an antioxidant N-acetyl-l-cysteine. These results indicate that I-α-PNP treatment may down-regulate the plasma membrane-localized CLDN5 by elevating the production of reactive oxygen species (ROS). The treatment with I-α-PNP increased the nuclear translocation of Forkhead box protein O1 (FoxO1), an oxidative stress-responsive transcription factor, and pretreating with a FoxO1 inhibitor ameliorated the decrease in CLDN5 mRNA. In addition, I-α-PNP treatment up-regulated the expression and secretion of matrix metalloproteinase-2 (MMP2) and MMP9, and the addition of an MMP inhibitor reversed the degradation of CLDN5 by I-α-PNP. Moreover, I-α-PNP treatment facilitated the activation of 26S proteasome-based proteolytic activity and pretreatment with an inhibitor of 26S proteasome, but not autophagy, suppressed the CLDN5 degradation by I-α-PNP. Accordingly, it is suggested that the down-regulation of CLDN5 by exposure to I-α-PNP is ascribable to suppression of the gene transcription due to FoxO1 nuclear translocation through ROS production and to acceleration both of the MMPs (MMP2 and MMP9)- and 26S proteasome-based proteolysis.

Molecular Mechanisms of Action of Novel Psychoactive Substances (NPS). A New Threat for Young Drug Users with Forensic-Toxicological Implications

Novel psychoactive substances (NPS) represent a severe health risk for drug users. Even though the phenomenon has been growing since the early 2000s, the mechanisms of action of NPS at the receptors and beyond them are still scarcely understood. The aim of the present study was to provide a systematic review of the updated knowledge regarding the molecular mechanisms underlying the toxicity of synthetic opioids, cannabinoids, cathinones, and stimulants. The study was conducted on the PubMed database. Study eligibility criteria included relevance to the topic, English language, and time of publication (2010–2020). A combined Mesh and free-text protocols search was performed. Study selection was performed on the title/abstract and, in doubtful cases, on the full texts of papers. Of the 580 records identified through PubMed searching and reference checking, 307 were excluded by title/abstract and 78 additional papers were excluded after full-text reading, leaving a total of 155 included papers. Molecular mechanisms of synthetic opioids, synthetic cannabinoids, stimulants, psychedelics, and hallucinogens were reviewed and mostly involved both a receptor-mediated and non-receptor mediated cellular modulation with multiple neurotransmitters interactions. The molecular mechanisms underlying the action of NPS are more complex than expected, with a wide range of overlap among activated receptors and neurotransmitter systems. The peculiar action profile of single compounds does not necessarily reflect that of the structural class to which they belong, accounting for possible unexpected toxic reactions.

Gender differences in tolerance to the hyperthermia mediated by the synthetic cathinone methylone

The toxidrome associated with death from the synthetic cathinones includes hyperthermia as part of the sympathomimetic syndrome. Here, we examine the gender differences in the development of tolerance to the hyperthermia mediated by the synthetic cathinone methylone. In addition to temperature changes, expression differences in genes encoding the uncoupling proteins (UCP) 1 & 3, and TGR5 in skeletal muscle (SKM) and brown adipose tissue (BAT) were examined. Male and female rats were treated weekly with methylone (10 mg/kg). The females developed a tolerance to the methylone-induced hyperthermia by week two of drug exposure. By the third week, females displayed a hypothermic response to methylone. Conversely, males continued to display a hyperthermic response up to and including week four. At week four, the males demonstrated a significantly lower hyperthermia and a complete tolerance seen at week five with no significant hyperthermia. Tissue samples collected after treatment on the sixth week indicate that chronic exposure to methylone reduced UCP1 expression in SKM and BAT of the female rats. Only the females displayed increased TGR5 expression in BAT. UCP3 expression increased in both the SKM and BAT of the males and females. The differences between responses in male and female subjects further demonstrate the need for gender studies in the toxicology associated with drugs with abuse potential.

Body temperature regulation and drugs of abuse

Phenethylamine-induced hyperthermia can occur following exposure to several different types of illicit stimulants, such as amphetamine, methamphetamine, 3,4-methylenedioxymethamphetamine ("Molly"), synthetic cathinones ("bath salts"), and N-methoxybenyl ("NBOMe"), to name a few. Peripheral norepinephrine release mediated by these sympathomimetic agents induces a double-edged sword of heat accumulation through β-adrenoreceptor-dependent activation of uncoupling protein (UCP1 and 3)-regulated thermogenesis and loss of heat dissipation through α₁-adrenoreceptor-mediated vasoconstriction. Additionally, thyroid hormones are important determinants of the capacity of thermogenesis induced by phenethylamines through the regulation of free fatty acid release and the transcriptional activation of a host of metabolic genes, including adrenergic receptors and mitochondrial uncoupling proteins. Here, we review the central and peripheral mechanistic "triggers" of phenethylamine-induced hyperthermia and outline potential pharmacologic interventions for managing phenethylamine-induced hyperthermia based on these recently discovered hyperthermia mediators.

Assessing the role of dopamine in the differential neurotoxicity patterns of methamphetamine, mephedrone, methcathinone and 4-methylmethamphetamine

Methamphetamine and mephedrone are designer drugs with high abuse liability and they share extensive similarities in their chemical structures and neuropharmacological effects. However, these drugs differ in one significant regard: methamphetamine elicits dopamine neurotoxicity and mephedrone does not. From a structural perspective, mephedrone has a β-keto group and a 4-methyl ring addition, both of which are lacking in methamphetamine. Our previous studies found that methcathinone, which contains only the β-keto substituent, is neurotoxic, while 4-methylmethamphetamine, which contains only the 4-methyl ring substituent, elicits minimal neurotoxicity. In the present study, it was hypothesized that the varying neurotoxic potential associated with these compounds is mediated by the drug-releasable pool of dopamine, which may be accessed by methamphetamine more readily than mephedrone, methcathinone, and 4-methylmethamphetamine. To test this hypothesis, l-DOPA and pargyline, compounds known to increase both the releasable pool of dopamine and methamphetamine neurotoxicity, were combined with mephedrone, 4-methylmethamphetamine and methcathinone. Methamphetamine was also tested because of its ability to increase releasable dopamine. All three regimens significantly enhanced striatal neurotoxicity and glial reactivity for 4-methylmethamphetamine. Methcathinone neurotoxicity and glial reactivity were enhanced only by l-DOPA. Mephedrone remained non-neurotoxic when combined with either l-DOPA or pargyline. Body temperature effects of each designer drug were not altered by the combined treatments. These results support the conclusion that the neurotoxicity of 4-methylmethamphetamine, methcathinone and methamphetamine may be differentially regulated by the drug-releasable pool of dopamine due to β-keto and 4-methyl substituents, but that mephedrone remains non-neurotoxic despite large increases in this pool of dopamine. This article is part of the Special Issue entitled 'Designer Drugs and Legal Highs.'